Cascade refrigeration system with variable speed CO₂ compressors
A highly efficient refrigeration system was required for the Yunnan International Logistics Port, especially for part load conditions. All equipment had to be able to operate at low cooling capacity. The solution: an R744 (CO₂)/R507A cascade system combining eight BITZER reciprocating compressors of the ECOLINE ME series (6PME) and five semi-hermetic screw compressors of the HS series (3x HSK95, 2x HSK74).
Reciprocating compressors for low temperature stage
The reciprocating compressors in the low temperature stage can withstand high standstill pressures, making them well suited for the large pressure differences and small compression ratios of CO₂ systems. Two of the eight compressors are equipped with frequency inverters for variable speed drive, allowing a flexible load response.
Screw compressors for high temperature stage
The screw compressors in the high temperature stage have large displacements and adjustable internal volume ratios. One of them is again equipped with variable speed drive in order to handle load changes flexibly.
Efficient through parallel operation and digital monitoring
The unit and system achieve a high degree of integration through the parallel operation of multiple compressors, which is monitored by a digital intelligent platform to ensure efficient operation. At the same time, the low-charge system does not store refrigerant at the high or medium pressure ends; instead, it uses low-pressure liquid storage and a low-rate supply. This reduces the required refrigerant charge by 30 to 50% compared to traditional systems.
